js add class syntax within parent element code example

Example: parent class and add element addclass

// html <div class="parentElm" id="addActive"></div>

// js
function toggleClass(){
  // get the properties of an element
  var element = document.getElementById("addActive");
  
//  check if the element have class list
  if (element.classList) {
    // add active class if true
   element.classList.toggle("active");
  } else {
   var classes = element.className.split(" ");
   var i = classes.indexOf("active");
  }
 }